Subsequent to the production of a workpiece it is common practice in quality assurance to inspect the workpiece on a measuring machine, such as a coordinate measuring machine, having a movable probe head.
In a conventional three-dimensional measuring machine, the probe head is supported for movement along three mutually perpendicular axes (in directions X, Y and Z). The probe head comprises a suitable transducer as a probe, for example for tactile or optical measurements, which is used to determine the position of the probe head relative to a base of the machine and to determine the coordinates of a measurement point on an object being approached by the probe.
The functionality of a conventional coordinate measuring machine is typically structured as follows:
The measuring machine is designed to satisfy certain performance requirements, such as size, measurement accuracy and speed. The machine dynamics is designed for allowing satisfaction of such requirements. A machine controller is provided for running the machine according to the required performance parameters, including machine calibration for meeting an overall set of machine specifications. Typically, a conventional coordinate measuring machine is provided with a system software package comprising a basic software package and one or more additional feature software packages accomplishing the basic package.
A conventional process for measuring an object with a measuring machine is structured as follows:
It is presupposed that CAD data of the object to be measured are available for preparation of the measurement. If this condition is satisfied, features of the object to be measured are selected. This regularly first implies choice of the way how the selected features shall be measured, and selection of a suitable probe system. If there is a need for a datum then a way for realization of the datum is selected. Finally in the preparation phase, a part programme is selected, which may imply different degrees of automation, ranging from completely manual to fully automated generation of the part programme.
After accomplishment of the preparation phase, the execution phase of a conventional measurement process comprises the following steps:
Depending on required measurement accuracy and further required measurement and performance parameters, in the beginning a suitable measuring machine is selected. Then typically the object to be measured is loaded into the measuring machine, accompanied by the steps of calibrating the selected probe system, setting up measuring machine parameters, particularly also a targeted measurement accuracy and speed. The last steps of the execution phase comprise executing the measurement part programme and, finally, determining deviations between the CAD data and the measurement data of the real part.
The preparation of a measuring machine for performing a measurement of an object takes a significant amount of time and efforts. Furthermore, precise measurements of features of objects of any kind require a variety of dedicated measurement tools or parts and availability of a large number of different measurement programmes.
DE 101 30 737 B4 discloses a system wherein a number of stations are used to measure and adjust cutting tools used on computer numerical control (CNC) machines. The units have measuring systems, controlled axes and are linked to local controllers that use local and remote software. The remote software is provided by a link over the internet to a central computer. The invention of DE 101 30 737 B4 is dedicated to solve the object of providing an adjustment device capable of performing a plurality of different measurement tasks in a flexible way and at low costs. For this purpose, according to DE 101 30 737 B4, a part of the system software is not resident on a local computer for device control, but on an external, central computer, thus reducing the requirements on the local control system. A user may be provided with remote software packages for measuring machines via the internet either for sale or for rent, or on any other basis, just only for the time when such “additional intelligence” is needed, this software being saved on and available from an external server.
Thus, system requirements to be realized on a user's site are reduced, but a support for improving the efficiency of working with the measuring machine, particularly in the course of steps for preparation of a measurement, is not provided.
JP 9 178 469 discloses a roundness measuring machine provided with an automatic part programme selection, wherein the part programme, in which a measurement procedure for a work piece is incorporated, is selected after a preceding measurement for a discrimination of a work piece fixing jig, e.g. in the form of a hole for identification purposes. In this way, risks of a damage of the measurement tool or part provoked by the potential of a wrong choice of the measurement tool or part are reduced. In a disclosed example, the part programme is selected depending on the size and the position, in an X-Y direction, of the hole as a jig discriminating formation part. However, also the invention of JP 9 178 469 does not provide further support for the steps of preparation of a measurement.